Soil pH has a stronger effect than arsenic content on shaping plastisphere bacterial communities in soil.

Microplastic (MP) pollution is widespread in various ecosystems and is colonized by microbes that form biofilms with compositions and functions. However, compared with aquatic environments, the soil environment has been poorly studied in terms of the taxonomic composition of microbial communities and the factors influencing the community structure of microbes in the plastisphere. In the present study, a microcosm experiment was conducted to investigate the plastisphere bacterial communities of MP (polyvinyl chloride, PVC) in soils with different pH (4.62, 6.5, and 7.46) and arsenic (As) contents (13 and 74 mg kg-1). Bacterial communities in the plastisphere were dominated by Proteobacteria and Firmicutes, with distinct compositions and structures compared with soil bacterial communities. Soil pH and As content significantly affected the plastisphere bacterial communities. Constrained analysis of principal coordinates and a structural equation model demonstrated that soil pH had a stronger influence on the dissimilarity and diversity of bacterial communities than did soil As content. Soil pH affected As speciation in soil and on MP. The concentration of dimethylarsinic acid (DMA) was significantly higher on MP than that in soil, indicating that As methylation occurred on MP. These results suggest that environmental fluctuations govern plastisphere bacterial communities with cascading effects on biogeochemical cycling of As in the soil ecosystems.